1. Field of the Invention
The present invention relates to rough surface formation, more particularly, to a method of forming a reflector having a rough surface which can be applied to reflective-type displays including a reflective LCD (liquid crystal display).
2. Description of the Prior Art
The surface roughness of an LCD reflector, especially its convex shape, is a very important factor in determining the viewing-angle range of brightness. In order to realize a bright LCD reflector, there have been proposed various methods for forming the rough surface of the LCD reflector.
Polishing the surface of a glass substrate is described in the paper "Reflective Multicolor LCD (II): Improvement in the Brightness" by Koizumi et al.(Proceedings of the SID Vol. 29/2, 1988 p. 159). In this method, the planar surface of a glass substrate is polished using an abrasive and then etched using a hydrofluoric acid solution to make the glass surface rough. The rough glass surface is covered with silver by vacuum evaporation.
Another method using a photolithography technique is disclosed in Japanese Patent Laid-open Publication No. Sho 58-125084. According to this method, after forming a photoresist pattern on a polyimide film, the polyimide film is etched using the photoresist pattern as a etching mask, causing the surface of the polyimide film to be rough. Subsequently, the rough surface of the polyimide film is covered with aluminum.
In the polishing method, however, it is difficult to desirably control the convex shape of the glass surface in order to accurately produce target reflective properties. The reason is that such a convex shape depends on the conditions of an abrasive, polishing, and etching with a hydrofluoric acid solution.
On the other hand, in the method using the photolithography technique, although the convex shape of the rough surface can be accurately controlled by using a mask pattern, it is fundamentally difficult to directly control the convex slope of the rough surface.